Optically sensitized photographic silver halide emulsions



United States Patent tion of Germany No Drawing. Filed Oct. 6, 1964,Ser. No. 402,006 Claims priority, applieitigg 4G02rmany, Oct. 26, 1963,

6 Claims. (21. 96-106) The invention relates to photographic silverhalide emulsions optically sensitized with merocyanine dyes at least oneof the heterocyclic nitrogen atoms of which is substituted by ahydroxypropyl sulfonic radical, the hydroxy group of which may besubstituted with an acyl group.

Merocyanine dyes, the nitrogen atoms in the heterocyclic rings of whichare substituted by alkyl radicals, are generally insoluble in water andalmost insoluble in organic solvents. This disadvantage can be overcomeby substituting at least one of the alkyl radicals attached to thenitrogen atoms of the heterocyclic rings by a watersolubilizing group,in particular sulfo groups. Although, the water solubility of theresulting dyes is sufficient and the dyes can be washed outsatisfactorily from the emulsion layers, the sensitizing effect isinsufficient. Particularly the decay of the senitization of thesesensitizing dyes is not steep enough towards longer wavelength so thatthe dark room safety of such sensitizers does not meet the requirements.

It is an object of the invention to provide new merocyanine dyes, atleast one of the heterocyclic atoms of which is substituted by ahydroxypropyl sulfonic acid group which may be acylated. Another objectis to provide methods for making these merocyanine dyes. Still anotherobject is to provide photographic emulsions sensitized with thesemerocyanine dyes. Other objects will become apparent from aconsideration of the following description and examples.

The above objects have been attained by providing merocyanine dyes inparticular dimethine merocyanines in which at least one of theheterocyclic nitrogen atoms is substituted by a hydroxypropyl sulfonicacid radical, the hydroxy group of which is preferably acylated. Thesedyes are excellent sensitizers for silver halide emulsions.

Especially suitable are merocyanines containing, as one of theheterocyclic groups, a benzoxazole or benzthiazole group in which thenitrogen atom is substituted with an oxypropyl sulfonic acid radicalacylated, if desired and in which the benzene rings of the radicals canbe substituted, for example, by halogen atoms, or alkyl preferably alkylhaving up to 5 carbon atoms, alkoxy the alkyl group of which having upto 5 carbon atoms or aryl groups such as phenyl or naphthyl, in the5-position and/or the 6- position.

. Particular utility exhibit sensitizers of the following formula:

(I) tfili cacfii wherein Y represents an oxygen or sulfur atom;

X represents an oxygen or sulfur atom or the groups N-R and CONR;

Z represents a hydrogen atom or preferably an acyl group, particularlyacyl groups derived from lower aliphatic acid having up to 5 carbonatoms such as acetyl, propionyl and the like;

R represents alkyl preferably lower alkyl having up to 5 carbon atomssuch as methyl or ethyl, aryl such as phenyl or naphthyl, preferablyphenyl, or aralkyl preferably phenyl alkyl such as benzyl or phenylethyl;

A represents hydrogen, halogen such as chlorine or bromine, alkylpreferably lower alkyl having up to 5 carbon atoms such as methyl orethyl, aryl preferably phenyl, aralkyl such as benzyl or phenyl ethyl oralkoxy group, the alkyl group of which having preferably up to 5 carbonatoms, hydroxy, carboxyl or esterified carboxyl in particular with loweraliphatic alcohols having up to 5 carbon atoms such as carbomethoxy orcarboethoxy, heterocyclic groupings, such as thienyl or furyl or one ormore of those substituents which are usuall in cyaniue chemistry,preferably in the 5-position and/or 6-position, A may further representan aryl ring, preferably a phenyl ring, fused to the benzene ring and inparticular in the 5,6-posi-tion, and

B represents a cation such as a hydrogen cation, a cation of alkali orearth alkali metals such as sodium, potassium or calcium or ammoniumcations. The nature of the cation is not critical and can be selected inaccordance with the requirements of the methods of preparation of thesensitizing dye.

The sensitizing dyes of the invention are prepared by quaternizing thenitrogenous heterocyclic bases which are usual in cyanine chemistry,such as Z-methylbenzoxazole, 2,5-dimethylbenzoxazole,Z-methyl-S-chlorobenzoxazole, 2-methylbenzthiazole, substitutedZ-methylbenzthiazoles with 3-chloro-2-hydroxy propane-l-sulfonic acid,which can be prepared as follows:

Epichlorohydrin is, as known from the literature (Ber. 61 (1928) page1354), reacted in a simple manner with acid sodium sulfite orpyrosulfite to form the salt of 3- chloro-2-hydroxypropane sulfonicacid. The free acid is obtained from the aqueous solution of this saltby using an ion exchange column. After evaporation of the water invacuo, this free acid is present as semi-solid substance.

In the reaction of 3-chloro-2-hydroxypropane-l-sulfonic' acid withZ-methylbenzthiazole or its derivatives substituted in the benzenenucleus (e.g. 2,5-dimethylbenzthiazole, 2,6 dimethylbenzthiazole,2,5,6-trimethylbenzthiazole, 2-methyl-5- or 6-methoxybenzthiazole or2-methyl- S-chlorobenzthiazole), hydrochloric acid is split off (thechlorohydrates of the benzthiazole bases may be isolated by sublimation)and the quaternary salts of Formula II are formed.

The quaternization of the benzoxazole bases can, for example, beperformed by heating 1 mol of 3-chloro-2- hydroxypropane-l-sulfonic acidwith 2 mols of benzoxazole base, for example, in tetralin. The tetralinand the benzoxazole hydrochloride formed in the reaction are distilledoff together.

Generally theresidue of the reaction can be treated with isopropanol andethyl acetate as solvent, to isolate the quaternary betains, forexample, those of Formula II, as hygroscopic substances. Occasionally,these betains appear to exist in the open form Ila, but the lattercompounds are converted back to the form represented by Formula II onfurther processing.

\ +1120 0 o 0 CH3 on, 4120 NH N omorronomsoan These reaction productsare then reacted according to common practice either directly withsuitable derivatives I of heterocyclic compounds to form the merocyaninedyes (see Example 3) or they are initially transformed into intermediateproducts, for example, those of the Formula III.

I OHz-CH-CHzSOr Since the condensation with diphenylformamidine iscarried out in the presence of carboxylic anhydrides, more especiallyacetic anhydride, the hydroxyl group of. the nitrogen substituent issimultaneously acylated, so that the products obtained have the FormulaIII. These intermediate products of type III can be condensed insuitable solvents, such as alcohol, pyridine or acetic anhydride, withthe addition of condensation agents, such as triethylamine or alkalimetal alcoholates. The compounds of type III react with compounds whichcontain reactive methylene groups (such as rhodanines, thiohydantoins orthiobarbituric acid) to form dimethine dyes.

The intermediate products, for example, the product III, can besynthesized as follows:

40 g. of the quaternary betains are dissolved on a steam bath in 100 cc.of acetic anhydride. 63 g. of diphenylformamidine are added and themixture heated for 30 minutes. The desired intermediate is precipitatedby addition of ethyl acetate as yellowish-orange powder.

The present invention includes sensitizing dyes which in principlecorrespond to Formula I, wherein however the benzthiazole or benzoxazolegroupings are replaced by other 5- or 6-membered heterocyclic ringswhich are usual in cyanine chemistry, for example, oxazoles, selenazole,oxazines, benzoxazines, thiazoles, benzselenazole, naphthoselenazoles,thiodiazoles, oxadiazoles, imidazoles, benzimidazoles, pyrimidines,pyridines, quinolines, isoquinolines, thiazolines or indolenines.

Preferred, however, are sensitizing dyes according to Formula I, moreparticular those in which the benzene ring is unsubstituted or issubstituted with methyl groups in the 5- and/or 6-position or chlorineatoms in the 5- position or in which further benzene nuclei are fused tothe benzene rings of the heterocyclic groupings.

The merocyanine dyes of the present invention are characterized by thefollowing advantages:

(a) Excellent sensitizing action both in black-and-white and colorphotographic silver halide emulsions;

(b) A very sharp decay of the sensitization curve to wards the region ofthe longer wavelength and in consequence thereof a high dark room safetyof the photographic material, sensitized by the present merocyanines;

(c) No coloring of the emulsions sensitized with the merocyanines; thedyes are washed out completely;

(d) The dyes can be prepared in a very simple manner.

Silver halide emulsion layers which contain silver chloride, silverbromide or mixtures thereof and which might additionally contain up to10 mol percent of silver iodidecan be used as light-sensitive layers.Gelatin is preferred as binder for the light-sensitive layers, but thiscan be wholly or partially replaced by other layer-forming, hy-

drophilic colloids, depending upon the properties which are required.Suitable, for example, are polyvinyl alcohol, polyvinyl pyrrolidone,starch or starch ether, alginic acid and derivatives thereof such assalts particularly with alkali metals, esters or amides, orcarboxymethyl cellulose and the like.

The dyes of the present invention are advantageously incorporated in thewashed and finished emulsion and should be uniformly distributedthroughout the emulsion. The methods of incorporating the dyes in anemulsion are simple and well known to those skilled in the art ofemulsion making. It is convenient to add the dyes from solution inappropriate solvents such 'as alcohols and phenols or in a mixture ofthose solvents with water. The solvent must be compatible with theemulsion and substantially free from any deleterious effect on thesilver halide emulsion. Water or methanol or a mixture thereof hasproven satisfactory as a solvent for the majority of the new dyes.

The concentration of the sensitizing dyes of the present invention inthe silver halide emulsion can vary widely, for example, from about 2 to200 mg. preferably 10 to 60 mg. per kg. of the emulsion. Theconcentration of the dye will vary according to the type oflight-sensitive material in the emulsion and according to sensitizationdesired. The suitable and optimal concentration for any given emulsionWill be apparent to those skilled in the art upon making the ordinarytests customarily used in the art of emulsion making.

The dyestulfs are in addition particularly insensitive to otheradditives which are commonly used, for example, wetting agents,stabilizers, bactericides, fungicides, hardeners and developers added tothe layer, and also to other additives, such as color couplers, in theirwater-soluble or emulsified form, and to other dyestuifs such asantihalo or filter dyes or in the silver-dye-bleach process, forexample, azo dyestuffs.

The dyes according to the invention are also suitable for the opticalsensitization of electrophotographic semiconductor layers, moreespecially zinc oxide layers. The sensitizing dyes may also be used foremulsions intended for use in silver dye bleach processes.

EXAMPLE 1 Sensitizing dye 1 I CH-CH" s N O Naossom-on-oooorra CH3Preparation.-The following starting compound is used:

onrorpoulsoaw o-coon,

6.7 g. of this compound are heated with 5.2 g. of l-phenyl-3-methylthiohydantion in cc. of ethanol and 10 cc. of triethylamine for50 minutes on a steam bath. The reaction solution'is filtered hot andether is added to the filtrate. The ether filtered off is mixed withcommon salt solution and the dye precipitates from the separated layer.It is suction-filtered, dried and recrystallized frommethanol/isopropanol. It has a melting point of 375 C. and sensitizedwith a maximum at 530/, with very high grain sensitivity. The sensitizerdoes not show any dyeing of a photographic layer.

NB-OaS-OHl-CHO C OCH;

Preparatin.-The dye is formed by heating 30 g. of the intermediateproduct mentioned in the preceding example with 25 g. of1-phenyl-3-ethylthiohydantion, 540 cc. of ethanol and 43 cc. oftriethylamine for 60 minutes on a steam bath. The dye spontaneouslyseparates out. It can be reacted to form the sodium salt, whichcrystallizes with 1 mol of water as shown by the analysis below.

Empirical formula: C H O N S NaH O. Calculated: C, 51.3%; H, 4.4%; O,22.0%; N, 7.2%; S, 11.0%. Found: C, 50.8%, 51.0%; H, 4.7%, 5.1%; O,20.9%, 21.2%; N, 7.3%; S, 10.7%, 10.9%.

The dye melts above 360 C., has an absorption maximum in methanol at 480and a sensitization maximum of 535,14.

EXAMPLE 3 sensitizing dye 3 oHoH s sf .1

NaOaS-CIL-OHOCOCH; Preparation-2.9 of the quaternary salt of theformula:

H2.CH0H.CHgS03(-) and 2.6 g. of the compound are refluxed in 30 cc. ofacetic anhydride and 5 cc. of triethylamine for 1 hour. The reactionmixture is poured into ether, the precipitated green grease is extractedby boiling with ether several times, dissolved in water and the dye isprecipitated with sodium chloride solution. The crude dye is trituratedwith ether and isopropanol and recrystallized from a mixture ofmethanol/isopropanol. It has a melting point of 342 C., an absorptionmaximum at 5251A and a sensitization maximum at 590 EXAMPLE 4sensitizing We 4 Nao.s-oH2-hHooo0H,

M.P. 375 C.

Preparation.-4.6 g. of the starting compound of Ex- EXAMPLE 5Sensitizing a'ye 5 Cells fir er} Preparation.-14.5 g. of theintermediate product:

COCH;

( JHgCHO C OCHaCHzSO;

10 g. of 1-pheny1-3-methylthiohydantoin, cc. of acetonitrile and 25 cc.of triethylamine are heated for 30 minutes on a steam bath. The dye canbe purified as described in Examples 1 or 2. Sensitization maximum at535 1.

EXAMPLE 6 sensitizing dye 6 Preparati0n.--The dye is prepared asdescribed in Example 2 from the intermediate product III, and 1-methyl-3-phenylthiohydantoin. The melting point is 381 C. and thesensitization maximum at 530a.

EXAMPLE 7 Sensitizing dye 7 CgHs OH:

I NaoascHioHoo0oH,

Preparatl'0n.9.2 g. of the intermediate product HI and 7.4 g. ofN-methyl-N-ethylthiobarbituric acid are heated in alcohol withtriethylamine for 30 minutes on a steam bath. The dye crystallizes outfrom the reaction mixture. It is purified by recrystallization twicefrom methanol, with addition of water. M.P. 385 C., sensitizationmaximum 495 1..

7 EXAMPLE 8 sensitizing dye 8 I H0 0 0 CH CHQSOaNfi Preparati0n.l0 g. ofthe intermediate product III, g. of 3-methyl-2-thio-4-oxazolidone, 100cc. of acetonitrile and 5 cc. of triethylamine are heated for 30 minuteson a steam bath. The reaction mixture is filtered off from a smallquantity of a precipitate and about 0.5 liter of ether is added to thefiltrate. After some time it is filtered again and approximately 100 cc.of saturated sodium chloride solution and cc. of water are added to thefiltrate. The dye is precipitated from the water- 'ether layer. It issuction-filtered after 24 hours, dried and recrystallized from a mixtureof methanol and isopropanol.

M.P. 285 C. The sensitization maximum of a silver chlorobromideemulsion, such as used for reproduction purposes is at 520p.

EXAMPLE 9 The following example will serve to illustrate the advantagesof the merocyanines of the present invention:

An ordinary photographic silver chlorobromide emulsion chemicallysensitized with gold (III) chloride and stabilized with phenylmercaptotetrazole was divided into 3 portions. following prior-artsensitizers A and B were then added in solutions in a mixture ofmethanol and water.

( O G B CHCH= f S W CnHB I SO Na.

The portions of the emulsion were then coated on a transparent supportsuch as polyethylene terephthalate and dried. The dried coatings wereexposed according to common practice to a stepped test wedge, the riseof the wedge being /2 per step. The exposed coatings were developed forabout 5 minutes in a photographic developer having the followingcomposition:

30 mg. of the sensitizing dye 2 and of the" the less satisfactory is thedark room safety. The devel- The dark room safety of the photographicmaterial containing the merocyanine of the invention is readily apparentfrom the above table. Similar results are obtained if the sensitizingdye 2 is replaced by any oher sensitizer of the present invention.

We claim:

1. A11 optically sensitive silver halide emulsion con taining asensitizing amount of a dimethine merocyanine dye having the followingformula rfli iij CH3 JHOZ CH2SO B wherein Y represents a bivalentradical of the group consisting of oxygen and sulfur; X stands for aradical of the group consisting of oxygen, sulfur, an imino radical ofthe formula and a carbonimido radical of the formula --CONR-;

Z represents a member of the group consisting of hydrogen and acyl;

R represents a group of the class consisting of alkyl having up to 5carbon atoms, phenyl, naphthyl and phenyl alkyl;

A stands for a substituent of the group consisting of hydrogen, alkylhaving up to 5 carbon atoms, phenyl, phenyl alkyl, alkoxy having up to 5carbon atoms, hydroxy, carboxyl, esterified carboxyl, heterocyclicgroups and a fused-on phenyl ring;

B stands for a cation.

2. An emulsion as defined in claim 1 in which the dye has the followingformula (IJcHE 3. An emulsion as defined claim 1 in which the dye hasthe following formula on-on N/ .1

(3H, N Naoas onrr inoooon 9 10 4. An emulsion as defined in claim 1 inwhich the dye 6. An emulsion as defined in claim 1 in which the dye hasthe following formula has the following formula CaHs S I s N CH CH011-011 S HaC- S N 0- f f N (3H3 (3H1 Na03S OHa (|3HoOOCH3 02H, Na0SCHzCH0COCH cm 5. An emulsion as defined in claim 1 in which the dyeReferences Cited by the Examiner has the following formula UNITED STATESPATENTS 2,304,981 12/1942 Wilmanns 96106 0 2,870,014 1/1959 Brooker eta1 96l06 S 2,895,955 7/1959 Haseltine et a1. 260240.5 CHCH 2,984,6645/1961 Fry et al. 260-2405 s I 3,177,210 4/1965 Rosenoff 96106 f FOREIGNPATENTS I 742,112 12/ 1955 Great Britain. NaOzS-CHrCHO o 0 OH;

NORMAN G. TORCHIN, Primary Examiner. M.P. 375 C. J. TRAVIS BROWN,Assistant Examiner.

1. AN OPTICALLY SENSITIVE SILVER HALIDE EMUSLION CONTAINING ASENSITIZING AMOUNT OF A DIMETHINE MEROCYANINE DYE HAVING THE FOLLOWINGFORMULA